1. Field of the Invention
The present invention relates to a Battery Management System (BMS) and a battery management method. More particularly, the present invention relates to a BMS of a vehicle utilizing electrical energy.
2. Description of the Related Art
Vehicles using a gasoline or diesel internal combustion engine have caused serious air pollution. Accordingly, efforts to develop electric or hybrid vehicles have recently been made to reduce air pollution.
An electric vehicle uses an electric motor run by electrical energy output by a battery. Since the electric vehicle mainly uses a battery formed of one battery pack including a plurality of rechargeable/dischargeable secondary cells, there is merit in that it has no emission gases and less noise.
A hybrid vehicle commonly refers to a gasoline-electric hybrid vehicle that uses gasoline to power an internal combustion engine and an electric battery to power an electric motor. Recently, hybrid vehicles using an internal combustion engine and fuel cells and hybrid vehicles using a battery and fuel cells have been developed. The fuel cells directly obtain electrical energy by generating a chemical reaction while hydrogen and oxygen are continuously provided.
In such a vehicle using an electric motor, the number of rechargeable batteries (cells) has been increased so as to improve a power source thereof, and a cell balancing control method capable of efficiently managing a plurality of coupled cells and packs is needed for a Battery Management System (BMS).
Particularly, a State of Charge (SOC) is measured by an Open Circuit Voltage (OCV) of key-on, and an initial SOC is estimated using an OCV table corresponding to the SOC and temperature. The SOC is then estimated by integrating a current to obtain the estimated initial SOC.
The battery estimate SOC is reset at a reset SOC corresponding to an SOC reset condition when the battery terminal voltage Vt, the battery current i, and the battery temperature T are satisfied by the SOC reset condition. Since the reset SOC may not correct reset estimate errors in the SOC reset condition, each SOC value corresponding to the SOC reset condition becomes the reset SOC. When the SOC reset condition correspond to overcharge threshold ranges or an over-discharge threshold range, an overcharge and over-discharge of the battery can occur due to the reset estimate error of the SOC reset condition.